This invention pertains to ferrous metal protecting compositions, and more particularly to single-package systems having long shelf lives.
Zinc-rich ferrous metal protecting coatings have been available for some time but in general they require two or three separate packages of the requisite ingredients since gelling, settling or other undesirable phenomena take place if a single package is used. Attempts to prepare a single package zinc-rich silicate coating are well known to those skilled in the art. The desirability for a single package zinc-rich silicate coating has been recognized for some years and recently a few have become available commercially. For example U.S. Pat. No. 3,653,930 discloses a single package zinc-rich coating based on the addition of low molecular weight amines to hydrolyzed ethyl silicate in conjunction with nitro compounds to prevent gassing. U.S. Pat. No. 3,660,119 exposes some of the problems inherent in amine-containing alkyl silicate zinc-rich coatings including loss of effectiveness with time on standing. This disclosure claims the use of strong bases, such as, sodium or potassium methoxide or ethoxide to impart stability to these compositions. U.S. Pat. No. 3,859,101 also uses low-molecular weight amines in a single package alkyl silicate zinc-rich coating and precludes gassing in the container by the addition of zinc chromate. However the use of low-molecular weight amines is undesirable because their volatility results in loss of effectiveness with time, and is a potential health hazard.